The successful treatment of chronic nonhealing wounds requires strategies that promote angiogenesis, collagen deposition, and re-epithelialization of the wound. Copper ions have been reported to stimulate angiogenesis; however, several applications of copper salts or oxides to the wound bed are required, leading to variable outcomes and raising toxicity concerns. We hypothesized that copper-based metal-organic framework nanoparticles (Cu-MOF NPs), referred to as HKUST-1, which are rapidly degraded in protein solutions, can be modified to slowly release Cu, resulting in reduced toxicity and improved wound healing rates. Folic acid was added during HKUST-1 synthesis to generate folic-acid-modified HKUST-1 (F-HKUST-1). The effect of folic acid incorporation on NP stability, size, hydrophobicity, surface area, and copper ion release profile was measured. In addition, cytotoxicity and in vitro cell migration processes due to F-HKUST-1 and HKUST-1 were evaluated. Wound closure rates were assessed using the splinted excisional dermal wound model in diabetic mice. The incorporation of folic acid into HKUST-1 enabled the slow release of copper ions, which reduced cytotoxicity and enhanced cell migration in vitro. In vivo, F-HKUST-1 induced angiogenesis, promoted collagen deposition and re-epithelialization, and increased wound closure rates. These results demonstrate that folic acid incorporation into HKUST-1 NPs is a simple, safe, and promising approach to control Cu release, thus enabling the direct application of Cu-MOF NPs to wounds.

The principle cause of cardiovascular disease (CVD) is atherosclerosis, a chronic inflammatory condition characterized by immunologically complex fatty lesions within the intima of arterial vessel walls. Dendritic cells (DCs) are key regulators of atherosclerotic inflammation, with mature DCs generating pro-inflammatory signals within vascular lesions and tolerogenic DCs eliciting atheroprotective cytokine profiles and regulatory T-cell (Treg) activation. Here, the surface chemistry and morphology of synthetic nanocarriers composed of poly(ethylene glycol)-bpoly(propylene sulfide) copolymers to enhance the targeted modulation of DCs by transporting the anti-inflammatory agent 1,25-dihydroxyvitamin D3-(aVD) and ApoB-100-derived antigenic peptide P210 are engineered. Polymersomes decorated with an optimized surface display and density for a lipid construct of the P-D2 peptide, which binds CD11c on the DC surface, significantly enhance the cytosolic delivery and resulting immunomodulatory capacity of aVD in vitro. Weekly lowdose intravenous administration of DC-targeted, aVD-loaded polymersomes significantly inhibit atherosclerotic lesion development in high-fat-diet-fed ApoE −/− mice. The results validate the key role of DC immunomodulation during aVD-dependent inhibition of atherosclerosis and demonstrate the therapeutic enhancement and dosage lowering capability of cell-targeted nanotherapy in the treatment of CVD.

Polymeric nanoparticles containing multiple amines and carboxylates have been frequently used in drug delivery research. Reproducible and controlled conjugation among these multifunctional biomaterials is necessary to achieve efficient drug delivery platforms. However, multiple functional groups increase the risk of unintended intramolecular/intermolecular reactions during conjugation. Herein, conjugation approaches and possible undesired reactions between multi-amine functionalized peptides, multi-carboxylate functionalized polymers, and anhydride-containing polymers [Poly(styrene-alt-maleic anhydride)-b-poly(styrene)] were investigated under different conjugation strategies (carbodiimide chemistry, anhydride ring-opening via nucleophilic addition elimination). Muti-amine peptides led to extensive crosslinking between polymers regardless of the conjugation chemistry. Results also indicate that conventional peptide quantification methods (i.e., o-phthalaldehyde assay, bicinchoninic acid assay) are unreliable. Gel permeation chromatography (GPC) provided more accurate qualitative and quantitative evidence for intermolecular crosslinking. Crosslinking densities were correlated with higher feed ratios of multifunctional peptides and carbodiimide coupling reagents. Selectively protected peptides (Lys-Alloc) exhibited no crosslinking and yielded peptide-polymer conjugates with controlled dispersity and molecular weight. Furthermore, anhydride ring-opening (ARO) nucleophilic addition elimination was successfully introduced as a facile yet robust peptide conjugation approach for cyclic anhydride-containing polymers.

Despite efforts to achieve tissue selectivity, the majority of systemically administered drug delivery systems (DDSs) are cleared by the mononuclear phagocyte system (MPS) before reaching target tissues regardless of disease or injury pathology. Previously, we showed that while tartrate‐resistant acid phosphatase (TRAP) binding peptide (TBP)‐targeted polymeric nanoparticles (TBP‐NP) delivering a bone regenerative Wnt agonist improved NP fracture accumulation and expedited healing compared with controls, there was also significant MPS accumulation. Here we show that TBP‐NPs are taken up by liver, spleen, lung, and bone marrow macrophages (Mϕ), with 76 ± 4%, 49 ± 11%, 27 ± 9%, and 92 ± 5% of tissue‐specific Mϕ positive for NP, respectively. Clodronate liposomes (CLO) significantly depleted liver and spleen Mϕ, resulting in 1.8‐fold and 3‐fold lower liver and spleen and 1.3‐fold and 1.6‐fold greater fracture and naïve femur accumulation of TBP‐NP. Interestingly, depletion and saturation of MPS using 10‐fold greater TBP‐NP doses also resulted in significantly higher TBP‐NP accumulation at lungs and kidneys, potentially through compensatory clearance mechanisms. The higher NP dose resulted in greater TBP‐NP accumulation at naïve bone tissue; however, other MPS tissues (i.e., heart and lungs) exhibited greater TBP‐NP accumulation, suggesting uptake by other cell types. Most importantly, neither Mϕ depletion nor saturation strategies improved fracture site selectivity of TBP‐NPs, possibly due to a reduction of Mϕ‐derived osteoclasts, which deposit the TRAP epitope. Altogether, these data support that MPS‐mediated clearance is a key obstacle in robust and selective fracture accumulation for systemically administered bone‐targeted DDS and motivates the development of more sophisticated approaches to further improve fracture selectivity of DDS.